Sky News has seen evidence that allegedly links Russia to an attempted coup in Montenegro.

It has been described as "the last piece in the jigsaw" by western intelligence sources.

Passport images belonging to one of the two main suspects link him to the Russian military and suggest he used an alias to plot the coup.

An old passport is issued in the name of Eduard Shishmakov. It describes him as the assistant military attache at the Russian Embassy in Poland.

Image:An old passport of Eduard Shirokov but in the name of Eduard Shishmakov

A more recent passport issued in August 2016, just two months before the attempted coup, has a photo of the same man, with the same birth date, but a different surname - Shirokov.

Western intelligence say it is proof Shirokov was a GRU officer and is connected to Moscow. They have described the coup attempt as "further evidence of aggressive Russian involvement in the heart of Europe".

Image:Eduard Shirokov is alleged to be an alias of one of the plotters

In a further development, Polish authorities have provided us with a statement claiming that Eduard Shirokov was thrown out of Poland:

"We would like to inform you that Eduard Vadimovich Shishmakov was identified as GRU and in October 2014 he was declared persona non grata by the Polish government," they said to us in a statement.

"This decision was taken after discovering his involvement in intelligence activities."

The Montenegrin Chief Special Prosecutor, Milivoje Katnic, said that the newer passport, with the Shirokov identity, could only have been issued with the help of state authorities:

"We now have evidence that nationalist structures from Russia are behind the coup attempt, but also that certain state bodies of Russia are involved, on a certain level," he told Montenegrin television.

"It is clear that the passport on another name could not have been issued, as well as everything else - to send (him) to Serbia and organise everything - without the involvement of certain structures.

"So, the passport was given to him by certain Russian state bodies under another name, and he is a member of the Russian military structures and his name is Eduard Shishmakov, that is his personal identity and we will charge him under that personal identity."

Image:The plot allegedly involved a plan to kill the then PM Milo Djukanovic

The attempted coup was planned for the evening of 16 October 2016 - the night of parliamentary elections in Montenegro.

Plotters allegedly planned to hide amongst a crowd of pro-Russian supporters protesting outside the Montenegrin parliament in the capital Podgorica.

They would then slip into the parliament, disguised as policemen, and open fire on the protesters, making it look as though the government had attacked its own people.

The plot, which allegedly involved a plan to assassinate the then prime minister Milo Djukanovic, was foiled hours before it was due to go into action and two Serbians were arrested by police.

Image:Russian Vladimir Popov has also been named as one of the plotters

In an interview with Sky News in Munich on Saturday, the current Montenegrin Prime Minister said he believed Vladimir Popov and Shirokov to be behind the coup:

"It is evident that those two individuals were organisers of a group that was supposed to carry out that coup. Yes, they have been identified as such," Dusko Markovich told me.

"There are certain structures in Russia which were preparing terrorist activity against Montenegro and their activities were aimed at halting Montenegro on its path towards NATO.

"They wanted to make a change in our democratic system. they didn't want to see us in NATO but they wanted to see those other parties that are anti-NATO parties, winning in the election.

"This was quite realistic and this threat was imminent. This was a threat not only to Montenegro but this was a threat to democracy."

Image:Sergei Lavrov described the allegations as 'unsubstantiated'

Russia has continually denied any involvement; on Monday foreign minister Sergei Lavrov described the allegations as "unsubstantiated". The Kremlin dismissed them as "absurd".